The present invention relates generally to fetal probes for monitoring the condition of a fetus in utero and more specifically to a fetal probe having an optical imaging device.
During in utero labor and delivery of a fetus, fetal probes are used to monitor the health of the fetus. Fetal probes having pulse oximeters are typically used to measure various blood characteristics including arterial blood oxygen saturation and pulse rate. Pulse oximetry sensors pass light through a portion of the fetus"" skin and photo-electrically detect pulsatile changes in the absorption of the light by the tissue. The detected light is then used to determine the characteristic of interest.
In order to achieve accurate measurements, the aforementioned sensing devices must maintain contact with the fetus at an appropriate part of the fetus"" body. The quality of the optical signal generated by the pulse oximeter sensor depends, in part, on the placement of the sensors on the fetus"" body and on the quality of optical coupling between the sensor and the patient. The quality of optical coupling is related to the amount of light emitted by the sensor that actually enters the fetus"" tissue and to the portion of the light received by the sensor that actually passes through the fetus"" blood-perfused tissue.
Tissue characteristics at the sensor site can affect the quality of the optical coupling between the sensor and the patient. The presence of hair or vernix on the skin will attenuate the light transmitted into the tissue by the sensor. For example, if the sensor is placed on a part of the fetus"" scalp the system may not be able to appropriately process the signal. Consequently, it is important that the physician position and orient the fetal probe at a proper place on the fetus.
One method of placing the fetal probe adjacent the fetus is through manual assessment of the womb to determine the orientation of the head of the fetus and depth of the fetus within the womb. Once the physician has determined the position of the fetus, the physician picks a line of entry and introduces the fetal probe along the line to try to place the fetal sensors on the fetus"" cheek. Unfortunately, the physician will only have tactile feedback in regards to the positioning of the sensors and will have no visual indication of the position of the fetal sensors relative to the fetus. If the physician has misassessed the position of the fetus and has not placed the fetal probe adjacent the fetus"" cheek, the physician will have a difficult time in correctly positioning the fetal probe.
Accordingly, what is needed are systems and methods that provide visual feedback to the physician as to the orientation and position of the fetal probe sensors within the womb.
The present invention provides devices, systems and methods for providing visual feedback to aid in the proper placement of a fetal sensor during a fetal oximetry monitoring procedure. An imaging device, such as an optical fiber or fiber bundle, optical conduits, CCD camera, or the like can be coupled to a distal portion of the fetal probe to visually image and/or illuminate the same or nearby region of tissue which the fetal sensor contacts. The images from the illuminated portion of tissue are transmitted through the imaging device to an optical viewing device such as a hand-held image viewing instrument, camera, or a video monitor.
In exemplary embodiments, the fetal probe will include fetal oximetry sensors that have a light emitter (e.g., an LED) and a light detecting sensor. The light emitter can emit an infrared light, a visible light, or the like. In exemplary configurations, the imaging device can be positioned adjacent the fetal oximetry sensors so as to provide a visual indication of the position of the fetal sensors relative to the fetus"" tissue.
In some arrangements, the LED can be used for emitting light for spectral pulse oximetry and for illuminating the fetus"" tissue for visual examination. In other configurations, a separate illumination source (e.g., such as an optical fiber coupled to a broad spectrum light source) can be used to provide illumination for the visualization of the region of the fetus.
The light detecting sensors of the present invention will typically be configured to sense the light emitted from the light emitter for pulse oximetry purposes. In most arrangements the imaging device will be a separate component coupled to the distal portion of the probe. However, in some arrangements, the light detecting sensors can be configured to detect the light for visualization purposes. For example, a light sensor can vary its mode of operation to be able to both detect pulse oximetry data and to provide visual images of the fetus. In such embodiments, the pulse oximetry light detecting sensor will have a dual function and the separate imaging device will not be needed.
In a first aspect, the present invention provides a fetal probe. The fetal probe comprises a body. A fetal sensor is coupled to the body. An imaging assembly is positioned on the body to provide visual feedback of the position of the fetal sensor.
In one embodiment, focusing optics are coupled to the fetal sensor so as to provide a field of view and depth of field for the imaging device. In an exemplary embodiment, the imaging device includes a bundle of optical fibers. The optical fiber bundle may work in close proximity to the tissue being viewed so that no focusing element at the distal end is necessary. In most embodiments, the optical fiber bundle comprises a coherent arrangement of fibers (plastic or glass) to provide an image with the necessary resolution. Typically, the fiber bundle has a flexibility and diameter (approximately 1 mm to 3 mm) such that the fiber bundle can follow the turns and bends of the fetal sensor cable. Consequently, the flexible fiber bundle provides minimal discomfort to the patient during insertion. The proximal ends of the fiber bundle are typically attached to an eye piece, CCD camera with a video display, or other viewing devices. In most configurations, the viewing device can be adapted to alter the image orientation and/or provide magnification.
Appropriate attachments could be provided to permit easy removal of the optical fiber from the fetal sensor after completion of placement in utero. In alternative embodiments, the fiber bundle can be left attached to the fetal sensor and the viewing device can be disconnected from the proximal end of the fiber bundle. Such an arrangement would be particularly helpful if the optical fiber bundle is used to verify continued good placement of the fetal probe during the progress of labor.
In a particular embodiment, the present invention provides a fetal probe having a light emitter and a dual mode light detector. The light detector can function in at least two modes. In a first mode the light detector can detect light from the light emitter to provide a visualization of a fetus. In the second mode the light detector processes spectral oximetry data.
In another aspect, the present invention provides a method for positioning a fetal probe adjacent a fetus. The method comprises placing a fetal probe having a fetal sensor in close proximity to the fetus. A portion of at least one of the fetus and in utero environment is imaged with an imaging device that is coupled to the fetal probe. The image(s) are transmitted to a viewing device so as to provide a visual indication of the position of the fetal sensor.
In yet another aspect, the present invention provides a method for positioning a fetal probe adjacent a fetus. The method comprises advancing a fetal probe having a fetal sensor into contact with the fetus. The position of the fetal sensor is monitored with an imaging device that is attached to the fetal probe. The position of the fetal probe is adjusted if it is determined that the position of the fetal sensor is not adequate for monitoring the fetus.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.